Introduction to global configuration files in Mybatis

Other concepts:

1. Interface programming

Primitive: Dao ------------------> DaoImpl

Mybatis Mapper -------------> xxMapper.xml

2. SqlSession represents a session with the database, it must be closed when it is used up

3. Both SqlSession and Connection are not thread-safe. You should get a new object every time you use it.

4. There is no implementation class for the Mapper interface, but mybatis will generate a proxy object for it. (Bind the interface with xml)

EmployeeMapper empMapper = sqlSession.getMapper(EmployeeMappper.getClass);

5. Two important configuration files

Mybatis global configuration file: database connection pool information, transaction manager information, system operating environment information, etc.

sql mapping file: save the mapping information of each sql statement: extract sql

Mybatis global configuration file

5. Mybatis can use the properties tag to import the content of the external properties configuration file

<properties resource="dbconfig.properties"></properties>

resource：引入类路径下的资源

url：引入网络路径下或者磁盘路径下的资源

6, settings configuration label for runtime behavior

	setting：用来设置每一个设置项

		name：设置项名

		value：设置项取值

7. typeAliases tag: alias processor: we can alias our Java types (recommend batch aliasing)

	<package name="com.xuan.mybatis.bean"/>

		package：为某个包下所有的类批量起别名

			name：指定包名（为当前包以及下面所有的子包的每一个类都起一个默认的别名（类型小写  ））

Note: In the case of batch aliasing, use the @Alisa annotation to specify a new alias for a certain type (to prevent two classes with the same name under the same package)

8. The environments tag: You can configure multiple environments for mybatis (development environment, test environment, etc.), default specifies the use of a certain environment

	environment：配置一个具体的环境信息；必须包含两个标签（transactionManager、dataSource），id代表当前环境唯一标识

	transactionManager：事务管理器

	dataSource：数据源

9. The databaseIdProvider tag: The type attribute that supports multiple data vendors is to get the database vendor's identification (Mysql, Oracle, SQL server...)

<databaseIdProvider>

<property name="Mysql" value="mysql"/>

<property name="Oracle" value="oracle"/>

<property name="SQL server" value="sqlserver"/>

</databaseIdProvider>

10, mappers tag: register the sql mapping to the global configuration

	mapper：注册一个sql映射		

		resource属性：引用类路径下的sql映射文件

		url属性：引用网络路径或磁盘路径下的sql映射文件

		class属性：引用（注册）接口

1. There is a sql mapping file, the mapping file name must be the same name as the interface, and it must be placed in the same directory as the interface;

2. There is no sql mapping file, all sql is written on the interface with annotations;

Recommended:

a) The more important and complex Dao interface is written using sql mapping file

b) The unimportant and simple Dao interface can use annotations for rapid development

Introduction to global configuration files in Mybatis

Mybatis global configuration file

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